Composition based on isotactic polypropylene obtained by metallocene catalysis and on grafted isotactic polypropylene obtained by ziegler-natta catalysis

ABSTRACT

The present invention relates to a composition comprising isotactic polypropylene homo- or copolymer obtained by metallocene catalysis (A), abbreviated to miPP, and isotactic polypropylene homo- or copolymer obtained by Ziegler-Natta catalysis (B), abbreviated to zniPP, and grafted. It also relates to a coextrusion tie comprising such a composition.  
     It also relates to a multilayer structure comprising a layer (L) comprising the preceding tie and, directly attached to this layer:  
     a nitrogen-comprising or oxygen-comprising polar layer (J), such as a layer of polyamide resin, of saponified ethylene/vinyl acetate copolymer (EVOH) or of polyester;  
     a layer (J) of an inorganic oxide deposited on a polymer, such as polyethylene (PE), poly(ethylene terephthalate) (PET) or EVOH; or  
     a metal or metalloplastic layer (J).

DESCRIPTION

[0001] The present invention relates to a composition comprising anisotactic polypropylene obtained by metallocene catalysis and anisotactic polypropylene obtained by Ziegler-Natta catalysis which isitself grafted. This composition is of use as coextrusion tie.

[0002] The coextrusion tie comprises grafted isotactic polypropyleneobtained by Ziegler-Natta catalysis, diluted in isotactic polypropyleneobtained by metallocene catalysis and optionally diluted in at least onepolyolefin (E) or in at least one polymer with an elastomeric nature (D)or in at least one blend of (E) and (D).

[0003] This coextrusion tie is of use, for example, in the manufactureof multilayer materials for packaging. Mention may be made of materialscomprising a film of polyamide (PA) homo- or copolymer and a film ofpolypropylene (PP) homo- or copolymer, it being possible for thepolypropylene film to be laminated onto the polyamide film or coextrudedwith the polyamide. The coextrusion tie is positioned between thepolypropylene film and the polyamide film for good adhesion of the PAand of the PP. These multilayer materials can be three-layer structuresPP/tie/EVOH or five-layer structures PP/tie/EVOH/tie/PP in which EVOHdenotes a copolymer of ethylene and of vinyl alcohol or a partially orcompletely saponified ethylene/vinyl acetate (EVA) copolymer.

[0004] Polypropylene is described in Kirk-Othmer, Encyclopaedia ofChemical Technology, 4th edition, Vol. 17, pages 784-819, John Wiley &Sons, 1996. Virtually all polypropylene sold is composed essentially ofisotactic polypropylene obtained by Ziegler-Natta catalysis possiblycontaining a small amount of atactic polypropylene.

[0005] U.S. Pat. No. 5,235,149 discloses packagings closed by capscomposed of an aluminium sheet, of a tie layer and of a polypropylenelayer. The tie layer of the cap is composed of various polymers graftedwith acrylic acid or maleic anhydride; the polymers can be chosen frompolyethylene, polypropylene, copolymers of ethylene and of vinyl acetateand copolymers of ethylene and of methyl acrylate.

[0006] Patent DE 19 535 915 A discloses a grafted polypropylene blockcopolymer for adhesively bonding polypropylene films to metal sheets.

[0007] Patent EP 689 505 discloses structures similar to those disclosedin the above patent but which are used to prepare food packagings.

[0008] Patent EP 658 139 discloses structures similar to those disclosedin the preceding patent but the tie is a grafted random polypropylenecopolymer comprising from 1 to 10% of comonomer, the Mw/Mn ratio isbetween 2 and 10 and the MFI (Melt Flow Index) is between 1 and 20 g/10min (at 230° C. under 2.16 kg).

[0009] It has now been found that the isotactic polypropylene homo- orcopolymer obtained by metallocene catalysis, subsequently abbreviated tomiPP, makes it possible to obtain tie compositions exhibiting anadhesion comparable to, indeed even better than, that of the ties notcomprising miPP. This polypropylene has an applicative advantage incomparison with the polypropylene obtained by Ziegler-Natta catalysiswhen it is used in coextrusion ties.

[0010] A subject-matter of the invention is a composition comprising:

[0011] 99 to 50% by weight of isotactic polypropylene homo- or copolymerobtained by metallocene catalysis (A);

[0012] 50 to 1% of a polymer or a blend of polymers, the said polymer orblend of polymers comprising from 50 to 100% by weight of isotacticpolypropylene homo- or copolymer obtained by Ziegler-Natta catalysis (B)grafted by a functionalized monomer and from 0 to 50% by weight ofpolymer (C) chosen from poly(1-butene) homo- or copolymer (C1),polystyrene homo- or copolymer (C2), polyethylene homo- or copolymer(C3) and their blends, the said polymer (C) being itself grafted by afunctionalized monomer, the percentages being based on the total of thepolymers (A), (B) and (C).

[0013] According to an embodiment of the composition, the functionalizedmonomer is unsaturated.

[0014] According to an embodiment of the composition, the functionalizedmonomer is taken from the group consisting of alkoxysilanes, carboxylicacids and their derivatives, acid chlorides, isocyanates, oxazolines,epoxides, amines and hydroxides.

[0015] According to an embodiment of the composition, the functionalizedmonomer is maleic anhydride.

[0016] According to an embodiment of the composition, at least onecomonomer of the polyethylene copolymer (C3) is chosen from α-olefinshaving from 3 to 30 carbon atoms, esters of unsaturated carboxylicacids, vinyl esters of saturated carboxylic acids, unsaturated epoxides,alicyclic glycidyl esters and ethers, unsaturated carboxylic acids,their salts and their anhydrides, and dienes.

[0017] According to an embodiment of the composition, the polyethylene(C3) is chosen from LDPE, HDPE, LLDPE, VLDPE, PE obtained by metallocenecatalysis, EPR and EPDM elastomers and their blends, ethylene/alkyl(meth)acrylate copolymers, ethylene/alkyl (meth)acrylate/maleicanhydride copolymers and ethylene/vinyl acetate/maleic anhydridecopolymers.

[0018] According to an embodiment of the composition, the latter isdiluted in a polyolefin (E) and/or a polymer with an elastomeric nature(D).

[0019] According to an embodiment of the composition, the amount ofpolyolefin (E) and/or of polymer with an elastomeric nature (D) isadvantageously from 20 to 1 000 and preferably 30 to 500 parts (byweight) per 10 parts of grafted isotactic polypropylene homo- orcopolymer obtained by Ziegler-Natta catalysis (B).

[0020] According to an embodiment of the composition, the proportions ofpolyolefin (E) and of polymer with an elastomeric nature (D) are suchthat the ratio (D)/(E) is between 0 and 1 and more particularly between0 and 0.5.

[0021] According to an embodiment of the composition, the latter isincluded in a coextrusion tie.

[0022] The invention concerns also the use of the composition above formanufacturing a coextrusion tie.

[0023] Another subject-matter of the invention is a multilayer structurecomprising a layer (L) comprising a composition as described above and,directly attached to the said layer (L):

[0024] a nitrogen-comprising or oxygen-comprising polar layer (J), suchas a layer of polyamide resin, of saponified copolymer of ethylene andof vinyl acetate (EVOH) or of polyester; or

[0025] a layer (J) of an inorganic oxide deposited on a polymer, such asPE, poly(ethylene terephthalate) (PET) or EVOH; or

[0026] a metal or metalloplastic layer (J).

[0027] According to an embodiment of the structure, the latter comprisesa polyolefin-based layer (K) directly attached to the layer (L), thelayer (L) thus being sandwiched between the said layer (K) and the layer(J).

[0028] The composition based on isotactic polypropylene homo- orcopolymer obtained by metallocene catalysis (A), abbreviated to miPP,additionally comprises at least one grafted isotactic polypropylenehomo- or copolymer obtained by Ziegler-Natta catalysis (B) andoptionally a grafted polymer (C), the said polymer (C) being chosen frompoly(1-butene) homo- or copolymer (C1), polystyrene homo- or copolymer(C2), polyethylene homo- or copolymer (C3), the blend of (C1) and (C2),the blend of (C1) and (C3), the blend of (C2) and (C3) and the blend of(C1), (C2) and (C3).

[0029] The isotactic polypropylene homo- or copolymer obtained bymetallocene catalysis (A), abbreviated to miPP, and the systems whichmake possible its synthesis are disclosed in the following references ofthe Applicant Company: U.S. Pat. No. 6,214,949, U.S. Pat. No. 5,968,854,EP 856 525, U.S. Pat. No. 5,789,502, EP 849 286, EP 802 206, U.S. Pat.No. 5,561,092 and EP 581 754.

[0030] The miPP (A) can, according to the above references, be acopolymer comprising between substantially 0 and 10% by weight of atleast one comonomer chosen from ethylene, butene, isobutylene and4-methylpentene.

[0031] As regards the polymer (B), it is an isotactic polypropylenehomo- or copolymer obtained by Ziegler-Natta catalysis. Mention may bemade, as comonomers, of:

[0032] α-olefins, advantageously those having from 3 to 30 carbon atoms.Examples of such α-olefins are the same as for (C3), except thatpolypropylene is replaced by ethylene in the list below,

[0033] dienes.

[0034] The polymer (B) can also be a copolymer comprising polypropyleneblocks.

[0035] Mention may be made, as example of polymer (B), of:

[0036] polypropylene,

[0037] blends of polypropylene and of EPDM or of EPR.

[0038] Advantageously, the polymer (B), which can be a blend of severalpolymers, comprises at least 50 mol % and preferably 75 mol % ofpropylene.

[0039] As regards the polymer (C3), it is chosen from polyethylene homo-or copolymers.

[0040] Mention may be made, as comonomers, of the following list:

[0041] α-olefins, advantageously those having from 3 to 30 carbon atoms.Examples of α-olefins having 3 to 30 carbon atoms comprise propylene,1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene,3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene, 1-eicosene, 1-docosene, 1-tetracosene,1-hexacosene, 1-octacosene and 1-triacontene. These α-olefins can beused alone or as a mixture of two or of more than two.

[0042] esters of unsaturated carboxylic acids, such as, for example,alkyl (meth)acrylates, it being possible for the alkyls to have up to 24carbon atoms. Examples of alkyl acrylate or methacrylate are inparticular methyl methacrylate, ethyl acrylate, n-butyl acrylate,isobutyl acrylate or 2-ethylhexyl acrylate.

[0043] vinyl esters of saturated carboxylic acids, such as, for example,vinyl acetate or propionate.

[0044] unsaturated epoxides. Examples of unsaturated epoxides are inparticular: aliphatic glycidyl esters and ethers, such as allyl glycidylether, vinyl glycidyl ether, glycidyl maleate, glycidyl itaconate,glycidyl acrylate or glycidyl methacrylate, and alicyclic glycidylesters and ethers, such as 2-cyclohexen-1-yl glycidyl ether, diglycidylcyclohexene-4,5-dicarboxylate, glycidyl cyclohexene-4-carboxylate,glycidyl 2-methyl-5-norbornene-2-carboxylate and diglycidylendo-cis-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate.

[0045] unsaturated carboxylic acids, their salts and their anhydrides.Examples of unsaturated dicarboxylic acid anhydrides are in particularmaleic anhydride, itaconic anhydride, citraconic anhydride andtetrahydrophthalic anhydride,

[0046] dienes, such as, for example, 1,4-hexadiene.

[0047] The polymer (C3) can comprise several comonomers.

[0048] Advantageously, the polymer (C3), which can be a blend of severalpolymers, comprises at least 50 mol % and preferably 75 mol % ofethylene. The density of (C3) is between 0.86 and 0.98 g/cm³. The MFI(abbreviation of Melt flow Index, here measured at 190° C. under 2.16kg) is advantageously between 1 and 1 000 g/10 min.

[0049] Mention may be made, as example of polymers (C3), of:

[0050] low density polyethylene (LDPE)

[0051] high density polyethylene (HDPE)

[0052] linear low density polyethylene (LLDPE)

[0053] very low density polyethylene (VLDPE)

[0054] polyethylene obtained by metallocene catalysis, that is to saythe polymers obtained by copolymerization of ethylene and of α-olefin,such as propylene, butene, hexene or octene, in the presence of asingle-site catalyst generally composed of a zirconium or titanium atomand of two cyclic alkyl molecules bonded to the metal. Morespecifically, the metallocene catalysts are usually composed of twocyclopentadiene rings bonded to the metal. These catalysts arefrequently used with aluminoxanes as cocatalysts or activators,preferably methylaluminoxane (MAO). Hafnium can also be used as metal towhich the cyclopentadiene is attached. Other metallocenes can includetransition metals from Groups IVA, VA and VIA. Metals from thelanthanide series can also be used.

[0055] EPR (ethylene/propylene rubber) elastomers;

[0056] EPDM (ethylene/propylene/diene) elastomers;

[0057] blends of polyethylene with an EPR or an EPDM;

[0058] ethylene/alkyl (meth)acrylate copolymers which can comprise up to60% by weight of alkyl (meth)acrylate and preferably from 2 to 40%;

[0059] ethylene/alkyl (meth)acrylate/maleic anhydride copolymersobtained by copolymerization of the three monomers, the proportions ofalkyl (meth)acrylate being identical to those above, the amount ofmaleic anhydride being from 0 to 10% and preferably from 0.2 to 6% byweight;

[0060] ethylene/vinyl acetate/maleic anhydride copolymers obtained bycopolymerization of the three monomers, the proportions of vinyl acetatebeing the same as those of alkyl (meth)acrylate in the above copolymersand the proportions of MAH being the same as those in the abovecopolymers.

[0061] As regards the polymer (C2), it is chosen from polystyrene orstyrene copolymers. Mention may be made, among the comonomers, by way ofexample, of dienes having from 4 to 8 carbon atoms.

[0062] As regards the polymer (C1), it is chosen from poly(1-butene) orthe copolymers of 1-butene with ethylene or another a-olefin having from3 to 10 carbon atoms, except the polypropylene (B) already mentioned.

[0063] As regards the monomer grafted to the polymer (C) and/or to thepolypropylene homo- or copolymer obtained by Ziegler-Natta catalysis(B), it is unsaturated. Moreover, that a monomer said functionalizedmeaning that it comprises at least one chemical function. Mention may bemade, by way of example, of alkoxysilanes, carboxylic acids and theirderivatives, acid chlorides, isocyanates, oxazolines, epoxides, aminesor hydroxides.

[0064] Mention may be made, among alkoxysilanes carrying anunsaturation, of:

[0065] vinyltrialkoxysilanes CH₂═CH—Si(OR)₃;

[0066] allyltrialkoxysilanes CH₂═CH—CH₂—Si (OR)₃;

[0067] (meth)acryloxyalkyltrialkoxysilanes (or (meth)acryisilanes)

[0068] CH₂═CR₁—CO—O—Y—Si(OR)₃ in which: R is an alkyl having from 1 to 5carbon atoms or an alkoxyl —R₂OR₃ in which R₂ and R₃ are alkyls havingat most 5 carbon atoms for the combination of R₂ and R₃; R₁ is ahydrogen or a methyl; Y is an alkylene having from 1 to 5 carbon atoms.

[0069] Use is made, for example, of vinylsilanes, such astrimethoxyvinylsilane, triethoxyvinylsilane, tripropoxyvinylsilane,tributoxyvinylsilane, tripentoxyvinylsilane ortris(β-methoxyethoxy)vinylsilane, allylsilanes, such astrimethoxyallylsilane, triethoxyallylsilane, tripropoxyallylsilane,tributoxyallylsilane or tripentoxyallylsilane, or acrylsilanes, such asacryloxymethyltrimethoxysilane, methacryloxymethylmethoxysilane,acryloxyethyltrimethoxysilane, methacryloxymethylmethoxysilane,acryloxyethyltrimethoxysilane, methacryloxyethyltrimethoxysilane,acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane,acryloxybutyltrimethoxysilane, methacryloxybutylmethoxysilane,acryloxyethyltriethoxysilane, methacryloxyethyltriethoxysilane,methacryloxyethyltripropoxysilane, acryloxypropyltributoxysilane ormethacryloxypropyltripentoxysilane.

[0070] Use may also be made of mixtures of these products. Use ispreferably made of:

[0071] vinyltrimethoxysilane (VTMO) CH₂═CH—Si—(OCH₃)₃;

[0072] vinyltriethoxysilane (VTEO) CH₂═CH—Si—(OCH₂CH₃)₃;

[0073] vinyltrimethoxyethoxysiiane (VTMOEO)

[0074] CH₂═CH—Si—(OCH₂OCH₂OCH₃)₃; and

[0075] (3-(methacryloxy)propyl)trimethoxysilane CH₂═C (CH₃)—C(O)O—(CH₂)₃—Si (OCH₃)₃

[0076] Examples of unsaturated carboxylic acids are those having 2 to 20carbon atoms, such as acrylic, methacrylic, maleic, fumaric and itaconicacids. The functional derivatives of these acids comprise, for example,the anhydrides, the ester derivatives, the amide derivatives, the imidederivatives and the metal salts (such as the alkali metal salts) of theunsaturated carboxylic acids.

[0077] Unsaturated dicarboxylic acids having 4 to 10 carbon atoms andtheir functional derivatives, particularly their anhydrides, areparticularly preferred grafting monomers.

[0078] These grafting monomers comprise, for example, maleic, fumaric,itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic,4-methylcyclohex-4-ene-1,2-dicarboxylic,bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic andx-methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acids and maleic,itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic,4-methylenecyclohex-4-ene-1,2-dicarboxylic,bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic andx-methylbicyclo[2.2.1]hept-5-ene-2,2-dicarboxylic anhydrides.

[0079] Examples of other grafting monomer comprise C₁-C₈ alkyl esters orglycidyl ester derivatives of unsaturated carboxylic acids, such asmethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate,glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethylfumarate, dimethyl fumarate, monomethyl itaconate and diethyl itaconate;the amide derivatives of unsaturated carboxylic acids, such asacrylamide, methacrylamide, maleic monoamide, maleic diamide, maleicN-monoethylamide, maleic N,N-diethylamide, maleic N-monobutylamide,maleic N,N-dibutylamide, fumaric monoamide, fumaric diamide, fumaricN-monoethylamide, fumaric N,N-diethylamide, fumaric N-monobutylamide andfumaric N,N-dibutylamide; the imide derivatives of unsaturatedcarboxylic acids, such as maleimide, N-butylmaleimide andN-phenylmaleimide; and metal salts of unsaturated carboxylic acids, suchas sodium acrylate, sodium methacrylate, potassium acrylate andpotassium methacrylate.

[0080] Various known processes can be used to graft a grafting monomeronto the polymer (C) and/or onto the polypropylene homo- or copolymerobtained by Ziegler-Natta catalysis (B).

[0081] For example, this can be carried out by heating it at hightemperature, approximately 150° C. to approximately 300° C., in thepresence or absence of a solvent, with or without a radical initiator.

[0082] Appropriate solvents which can be used in this reaction arebenzene, toluene, xylene, chlorobenzene or cumene, inter alia.

[0083] Appropriate radical initiators which can be used comprise t-butylhydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide,di(t-butyl) peroxide, t-butyl cumyl peroxide, dicumyl peroxide,1,3-bis(t-butylperoxyisopropyl)benzene, acetyl peroxide, benzoylperoxide, isobutyryl peroxide, bis(3,5,5-trimethylhexanoyl) peroxide andmethyl ethyl ketone peroxide.

[0084] The polymer (C) and/or the polypropylene homo- or copolymerobtained by Ziegler-Natta catalysis (B) can be dry or melt preblendedand can then be grafted in the molten state or in solution in a solvent.They can also be added separately to a device for bringing into contactand blending (for example, an extruder) with the grafting monomer andthe radical initiator. Use may be made of the usual mixing and blendingdevices of the thermoplastics industry.

[0085] The amount of grafting monomer can be appropriately chosen but itis preferably from 0.01 to 10%, preferably 0.1 to 5%, with respect tothe weight of the composition comprising zniPP (B) and optionallycomprising the polymer (C) to be grafted. The amount of grafted monomeris determined by quantitatively determining the succinic functionalgroups by FTIR spectroscopy.

[0086] The grafted isotactic polypropylene obtained by Ziegler-Nattacatalysis (B) is manufactured:

[0087] either by grafting a blend comprising at least (B) and optionallyat least one polymer (C) chosen from (C1), (C2), (C3) and their blend.Advantageously, the proportion of (B) is at least 50% and preferably 70%by weight of the blend to be grafted;

[0088] or by grafting the isotactic polypropylene obtained byZiegler-Natta catalysis (B) and then optionally blending it with atleast one polymer (C) itself grafted and chosen from (C1), (C2), (C3)and their blend. In this case, the grafting monomer used to graft thezniPP (B) can be identical to or different from that used to graft thepolymer (C).

[0089] This grafted isotactic polypropylene obtained by Ziegler-Nattacatalysis (B) is then diluted in isotactic polypropylene obtained bymetallocene catalysis (A) and optionally in at least one polyolefin (E)or one polymer with an elastomeric nature (D) or in a blend of (E) and(D).

[0090] This is because the invention also relates to a coextrusion tiecomprising:

[0091] isotactic polypropylene obtained by metallocene catalysis (A);

[0092] grafted isotactic polypropylene home- or copolymer obtained byZiegler-Natta catalysis (B) and optionally grafted polymer (C); and

[0093] at least one polyolefin (E) or at least one polymer with anelastomeric nature (E) or at least one blend of (E) and (D).

[0094] The polyolefin (E) can be chosen from polymers (C) and isotacticpolypropylene obtained by metallocene catalysis (A).

[0095] The polymer (D) is a polymer with an elastomeric nature, that isto say that it can be:

[0096] (i) an elastomer in the sense of Standard ASTM D412, meaning thatit can be drawn at ambient temperature to two times its width, can beheld thus for 5 minutes and can then return to its starting size, towithin less than about 10%, when it is released; or

[0097] (ii) a polymer which does not have exactly the abovecharacteristics but which can be drawn and can return substantially toits starting size.

[0098] The MFI of (D) is advantageously between 0.1 and 50 g/10 min.

[0099] Mention may be made, as example of polymers (D), of:

[0100] EPR (ethylene/propylene rubber) polymers and EPDM(ethylene/propylene/diene) polymers;

[0101] polyethylenes obtained by metallocene catalysis and with adensity of less than 0.910 g/cm³;

[0102] polyethylenes of VLDPE type (very low density);

[0103] styrene elastomers, such as SBR (styrene/butadiene rubber)elastomers, styrene/butadiene/styrene (SBS) block copolymers,styrene/ethylene/butene/styrene (SEBS) block copolymers andstyrene/isoprene/styrene (SIS) block copolymers;

[0104] copolymers of ethylene and of at least one ester of unsaturatedcarboxylic acid (already defined above for (C3));

[0105] copolymers of ethylene and of at least one vinyl ester ofsaturated carboxylic acid (already defined above for (C3)).

[0106] The amount of isotactic polypropylene obtained by metallocenecatalysis (A) and optionally of polyolefin (E) and/or of polymer with anelastomeric nature (D) can be from 20 to 1 000 and preferably 60 to 500parts (by weight) per 10 parts of grafted isotactic polypropyleneobtained by Ziegler-Natta catalysis (B). Use is advantageously made ofthe isotactic polypropylene obtained by metallocene catalysis (A) andthe polyolefin (E). The preferred proportions are such that the ratio ofthe amount of polyolefin (E) to the isotactic polypropylene obtained bymetallocene catalysis (A) is between 0 and 1 and more particularlybetween 0 and 0.5.

[0107] The tie of the invention can be manufactured by the usual meansfor thermoplastics by melt blending the various constituents in Buss®twin-screw extruders, mixers or roll mills.

[0108] The tie of the invention can also comprise various additives,such as antioxidants, ultraviolet absorbers, antistatic agents,pigments, dyes, nucleating agents, fillers, slip agents, lubricants,flame retardants and antiblocking agents.

[0109] As regards the multilayer structure according to the presentinvention, it comprises a layer (L) comprising the abovedescribed tieand, directly attached to this layer, a layer (J) which can be:

[0110] (i) a layer of oxygen-comprising or nitrogen-comprising polarresin,

[0111] (ii) a layer of an inorganic oxide deposited on a polymer, suchas polyethylene (PE), poly(ethylene terephthalate) (PET) orethylene/vinyl alcohol (EVOH) copolymer, or

[0112] (iii) a metal or metalloplastic layer.

[0113] Examples of polar resins which are preferred in the layer (J) arepolyamide resins, a saponified copolymer of ethylene and of vinylacetate, and polyesters.

[0114] More specifically, these polar resins comprise syntheticlong-chain polyamides having structural units of the amide group in themain chain, such as PA-6, PA-6,6, PA-6,10, PA-11 and PA-12; a saponifiedcopolymer of ethylene and of vinyl acetate having a degree ofsaponification of approximately 90 mol % to 100 mol %, obtained bysaponifying an ethylene/vinyl acetate copolymer having an ethylenecontent from approximately 15 mol % to approximately 60 mol %;polyesters, such as poly(ethylene terephthalate), poly(butyleneterephthalate) or poly(ethylene naphthenate); and blends of theseresins.

[0115] The layer of inorganic oxide can, for example, be silica,deposited on a layer of PE, of PET or of EVOH. In this case, thestructure according to the invention therefore successively comprises: atie layer comprising the composition according to the invention attachedto an SiO₂ (or SiO_(x)) layer, itself deposited on a layer of PE, of PETor of EVOH.

[0116] The metal layer can, for example, be a film or a sheet of ametal, such as aluminium, iron, copper, tin and nickel, or an alloycontaining at least one of these metals as predominant constituent. Thethickness of the film or of the sheet is, for example, fromapproximately 0.01 to approximately 0.2 mm. It is common practice todegrease the surface of the metal layer before laminating the tieaccording to the invention thereon. This layer (J) can also be ametalloplastic layer, such as, for example, a sheet of PET covered withaluminium.

[0117] It would not be departing from the scope of the invention if thepreceding structure were combined with other layers.

[0118] The invention also relates to the preceding structure combinedwith a polyolefin-based layer (K) on the side of the tie layer (L) whichhas remained free, the tie layer (L) thus making possible the adhesionof the layers (J) and (K) to one another. The structure defined here isof the form Layer (K)/Layer (L)/Layer (J). The polyolefin of the layer(K) can be chosen from the polymers (C) defined above.

[0119] These structures are of use in preparing packagings, for examplerigid hollow bodies, such as bottles or jars, flexible bags ormultilayer films.

[0120] The structures according to the invention are, for example, ofthe following form, with the tie comprising the composition according tothe invention:

[0121] Layer (K)/Layer (L)/Layer (J)/Layer (L)/Layer (K):PE/tie/EVOH/tie/PE or PP/tie/EVOH/tie/PP or PE/tie/EVOH/tie/PP

[0122] Layer (K)/Layer (L)/Layer (J): PE/tie/EVOH or PE/tie/PA orPP/tie/PA

[0123] These structures and these packagings can be manufactured bycoextrusion, lamination, extrusion-blow moulding and coating.

[0124] The following products were used in carrying out the followingtests and comparative tests:

[0125] miPP 1: Isotactic polypropylene copolymer obtained by metallocenecatalysis, comprising 3.5% of ethylene.

[0126] Density=0.900 g/cm³, MFI=7 g/10 min (at 230° C. under 2.16 kg).

[0127] miPP 2: Isotactic polypropylene copolymer obtained by metallocenecatalysis, comprising 3.5% of ethylene.

[0128] Density=0.900 g/cm³, MFI=8 g/10 min (at 230° C. under 2.16 kg).

[0129] miPP 3: Isotactic polypropylene copolymer obtained by metallocenecatalysis, comprising 5% of ethylene.

[0130] Density=0.900 g/cm³, MFI=2.5 g/10 min (at 230° C. under 2.16 kg).

[0131] PP 3020 GN3: Random polypropylene copolymer obtained byZiegler-Natta catalysis (zniPP).

[0132] Density=0.900 g/cm³, MVI (Melt Volume Index)=2 cm³/10 min (at230° C. under 2.16 kg).

[0133] PP terpo: Random polypropylene terpolymer.

[0134] Density=0.900 g/cm³, MVI=5 cm³/10 min (at 230° C. under 2.16 kg).

[0135] MAH: Maleic anhydride.

[0136] PPAM2: Polypropylene grafted with maleic anhydride, comprising2.5% of MAH.

[0137] MFI=40 g/10 min (at 190° C. under 325 g).

[0138] LLDPE: Linear low density polyethylene.

[0139] Density=0.900 g/cm³, MFI=3 g/10 min (at 190° C. under 2.16 kg).

[0140] EPR: Ethylene/Propylene Rubber.

[0141] Density=0.870 g/cm³, MFI=5 g/10 min (at 190° C. under 2.16 kg).

[0142] mPE: Polyethylene obtained by metallocene catalysis.

[0143] Density=0.870 g/cm³, MFI=5 g/10 min (at 190° C. under 2.16 kg).

[0144] The products are manufactured in a corotating twin-screw extruderof Leistritz® type.

[0145] The extruder comprises 8 regions numbered Z1 to Z8, the region Z8being situated at the end of the extruder where the grafted productsexit. The processing is carried out at the usual temperatures known to aperson skilled in the art.

[0146] The maleic anhydride and the polypropylene to be grafted areintroduced into the region Z1 via two separate weight metering devices.

[0147] The radical initiator, pure or diluted in an appropriate solvent,is introduced via a metering pump into the region Z2. The temperaturesin the regions Z3, Z4 and Z5 are at least sufficient for 99.9% of theradical initiator to react before the region Z6. The initiator used is2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or DHBP (Luperox® 101). Theresidues from the radical initiator, the solvent and the unreactedmaleic anhydride are degassed under vacuum in the region Z6.

[0148] The throughput for extrusion at the outlet of the region Z8varies, according to the screw rate imposed, between 12 and 15 kg/h. Thelace is granulated after cooling.

[0149] Cast technology was then used to produce a structure comprising 5layers, successively and respectively PP/tie/EVOH/tie/PP, in which:

[0150] PP denotes a layer of isotactic polypropylene obtained byZiegler-Natta catalysis (zniPP),

[0151] tie denotes a layer comprising the composition defined in Table 1with CP1 to CP4, the comparatives from 1 to 4 and EX1 to EX3, theexamples from 1 to 3 according to the invention, and

[0152] EVOH denotes a layer of ethylene/vinyl alcohol copolymer.

[0153] The thicknesses of the successive layers are respectively, in μm:20/10/10/10/50.

[0154] The peel strength between the 10-μim tie layer and the 10-μm EVOHlayer, in the direction of the 20-μm PP layer (CASE 1), and between the10-μm tie layer and the 10-μm EVOH layer, in the direction of the 50-μmPP layer (CASE 2), was subsequently measured.

[0155] The peel strength is expressed in N/15 mm at a drawing rate of200 mm/min at t=0, that is to say immediately after the structure hasbeen prepared, and at t=8, that is to say 8 days after the structure hasbeen prepared. The tie compositions in % by weight, the peel strengthsat t=0 and t=8 days, and the standard deviations (σ) at t=0 (σ0) and t=8days (σ8) are given in Table 2. TABLE 1 Composition of the Tie (A) (%)(E) (%) (B) (%) CP1 PP 3020GN3 74 LLDPE 20 PPAM2 6 CP2 PP 3020GN3 74 EPR20 PPAM2 6 CP3 PP 3020GN3 74 mPE 20 PPAM2 6 CP4 PP Terpo 74 mPE 20 PPAM26 EX1 miPP 1 74 mPE 20 PPAM2 6 EX2 miPP 2 74 mPE 20 PPAM2 6 EX3 miPP 374 mPE 20 PPAM2 6

[0156] TABLE 2 CASE 1 CASE 2 Peel Peel Peel Peel strength strengthstrength strength at t = 0 at t = 8 at t = 0 at t = 8 (N/15 mm) σ0 (N/15mm) σ8 (N/15 mm) σ0 (N/15 mm) σ8 CP1 4.99 0.61 6.33 0.39 1.83 0.06 3.270.1 CP2 5.69 0.35 7.3 0.12 2.6 0.11 4.28 0.22 CP3 5.71 0.62 7.3 0.4 2.760.15 4.20 0.33 CP4 5.75 0.1 6.69 0.05 2.4 0.1 4.35 0.05 EX1 5.44 0.096.94 0.07 2.63 0.04 4.91 0.04 EX2 5.6 0.13 7.02 0.12 2.73 0.07 4.87 0.14EX3 5.76 0.29 7.11 0.25 2.60 0.05 4.02 0.08

1. A composition comprising: 99 to 50% by weight of isotacticpolypropylene homo- or copolymer obtained by metallocene catalysis (A);50 to 1% of a polymer or a blend of polymers, the polymer or blend ofpolymers comprising (i) from 50 to 100% by weight of isotacticpolypropylene homo- or copolymer obtained by Ziegler-Natta catalysis (B)grafted by a functionalized monomer; and (ii) from 0 to 50% by weight ofa polymer (C) comprising a poly(1-butene) homo- or copolymer (C1), apolystyrene homo- or copolymer (C2), or a polyethylene homo- orcopolymer (C3) and their blends, said polymer (C) being itself graftedby a functionalized monomer, the percentages being based on the total ofthe polymers (A), (B) and (C).
 2. The composition according to claim 1,wherein the functionalized monomer is unsaturated.
 3. The compositionaccording to claim 1, wherein the functionalized monomer is analkoxysilane, a carboxylic acid or its derivative, an acid chloride, anisocyanate, an oxazoline, an epoxide, an amine or a hydroxide.
 4. Thecomposition according to claim 1, wherein the functionalized monomer ismaleic anhydride.
 5. The composition according to claim 1, wherein atleast one comonomer of the polyethylene copolymer (C3) is an α-olefinshaving from 3 to 30 carbon atoms, an ester of an unsaturated carboxylicacid, a vinyl ester of a saturated carboxylic acid, an unsaturatedepoxide, an alicyclic glycidyl ester or ether, an unsaturated carboxylicacid, or its salts or its anhydrides, or a diene.
 6. The compositionaccording to claim 1, wherein the polyethylene (C3) is LDPE, HDPE,LLDPE, VLDPE, PE obtained by metallocene catalysis, EPR or an EPDMelastomer or a blend of EPDM elastomers, an ethylene/alkyl(meth)acrylate copolymer, an ethylene/alkyl (meth) acrylate/maleicanhydride copolymer or an ethylene/vinyl acetate/maleic anhydridecopolymer.
 7. The composition according to claim 1, further comprising apolyolefin (E) and/or a polymer with an elastomeric nature (D) intowhich said composition is diluted.
 8. The composition according to claim7, in which the amount of polyolefin (E) and/or of polymer with anelastomeric nature (D) is advantageously from 20 to 1000 parts (byweight) per 10 parts of grafted isotactic polypropylene homo- orcopolymer obtained by Ziegler-Natta catalysis (B).
 9. The compositionaccording to claim 8, wherein the amount of polyolefin (E) and/or ofpolymer with an elastomeric nature (D) is 30 to 500 parts (by weight)per 10 parts of grafted isotactic polypropylene homo- or copolymerobtained by Ziegler-Natta catalysis (B).
 10. The composition accordingto claim 7, in which the proportions of polyolefin (E) and of polymerwith an elastomeric nature (D) are such that the ratio (D)/(E) isbetween 0 and
 1. 11. The composition according to claim 10, in which theproportions of polyolefin (E) and of polymer with an elastomeric nature(D) are such that the ratio (D)/(E) is between 0 and 0.5.
 12. Acoextrusion tie comprising the composition according to claim 1
 13. Amethod for manufacturing a coextrusion tie comprising admixing thecomposition of claim 1 with at least one of an antioxidant, anultraviolet absorber, an antistatic agent, a pigment, a dye, anucleating agent, a filler, a slip agent, a lubricant, a flame retardantor an antiblocking agent.
 14. A multilayer structure comprising a layer(L) comprising a composition according to claim 1, directly attached tothe layer (L): a nitrogen-comprising or oxygen-comprising polar layer(J), or a layer (J) of an inorganic oxide deposited on a polymer; or ametal or metalloplastic layer (J).
 15. The multilayer structureaccording to claim 14, wherein said nitrogen-comprising oroxygen-comprising layer is a layer of polyamide resin, of saponifiedcopolymer of ethylene and of vinyl acetate (EVOH) or of polyester; 16.The multilayer structure according to claim 14, wherein said polymeronto which said inorganic oxide layer (J) is deposited is PE,poly(ethylene terephthalate) (PET) or EVOH
 17. The multilayer structureaccording to claim 14, comprising a polyolefin-based layer (K) directlyattached to the layer (L), the layer (L) thus being sandwiched betweenthe layer (K) and the layer (J).